feat(sdk-core): add sync HTTP-client warm-up to SdkWarmUp.prime() for CRaC priming by joviegas · Pull Request #7080 · aws/aws-sdk-java-v2

joviegas · 2026-06-26T00:08:45Z

Motivation and Context

This change adds the second half of the hybrid priming approach: one real GET per sync HTTP client on the classpath, so that network path is JIT-compiled into the CRaC snapshot. It also adds the region/endpoint resolution shared with the future async warm-up.

Modifications

SdkWarmUp.prime() now runs the per-service providers and then the HTTP-client warm-up, both inside the existing idempotency guard. The HTTP-client warm-up is best-effort: a network failure during init is logged and swallowed so the rest of priming completes.

New internal types in sdk-core:

RegionEndpointResolver (internal.crac): resolves the region from the aws.region system property, then AWS_REGION, then AWS_DEFAULT_REGION, then us-east-1, and builds https://sts.<region>.amazonaws.com/. It reads system properties and environment variables, and avoids the SDK region-resolution chain (IMDS, profile file) during priming. The region is URL-encoded into the host the same way Region.of(String) does.
SyncHttpClientWarmer (internal.http.loader): discovers every sync SdkHttpService through the existing package-private SdkServiceLoader, builds each client, sends the warm-up GET, drains the response body, and closes the client. It lives in this package because SdkServiceLoader is package-private.
WarmUpRequest: describes the warm-up request (a GET) and converts it to an SdkHttpRequest.
WarmUpDiscovery: the discover-and-iterate loop shared by the per-service and HTTP-client warm-up. It skips an element that fails to load or run, including LinkageError (a client jar present without its transitive dependencies), so one broken element does not stop the others.
HttpClientWarmer interface plus HttpWarmupInvoker / ClasspathHttpWarmupInvoker: prime() calls one invoker that owns the set of warmers. The async warmer is added to that set later without changing SdkWarmUp or SyncHttpClientWarmer.

Testing

Added Junits test

Screenshots (if appropriate)

Types of changes

Bug fix (non-breaking change which fixes an issue)
[x ] New feature (non-breaking change which adds functionality)

License

I confirm that this pull request can be released under the Apache 2 license

… CRaC priming

joviegas · 2026-06-26T17:15:51Z

+public class Apache5HttpClientWarmUpTest {
+
+    @Rule
+    public WireMockRule mockServer = new WireMockRule(0);


We have a test for each HTTP client instead of a shared suite in test/http-client-tests. A shared suite there would create a cyclic dependency, because sdk-core has test dependencies on apache-client and netty-nio-client (sdk-core -> apache-client -> http-client-tests -> sdk-core). I filed JAVA-9020 to refactor this on master; once fixed, these tests can move to test/http-client-tests as a single SyncHttpClientWarmUpTestSuite shared across all HTTP clients.

A separate centralized package would be great, but maybe we can have a dedicated test package for testing CRaC components instead of using http-client-tests

joviegas · 2026-06-26T17:16:21Z

        <version>${awsjavasdk.version}</version>
        <scope>test</scope>
    </dependency>
+    <dependency>


Same as https://github.com/aws/aws-sdk-java-v2/pull/7080/changes#r3482981849

dagnir · 2026-06-26T19:57:04Z

+    }
+
+    // AWS_DEFAULT_REGION is an environment-variable-only fallback with no system-property equivalent.
+    private static final class AwsDefaultRegionEnvVar implements SystemSetting {


AFAIK, we don't use AWS_DEFAULT_REGION for determining endpoints in the SDK (only DefaultsMode). Should we leave this out?

dagnir · 2026-06-26T20:06:20Z

+     */
+    public URI stsEndpoint() {
+        // URL-encode the region before putting it in the host, same as Region.of(String).
+        return URI.create("https://sts." + SdkHttpUtils.urlEncode(resolveRegion()) + ".amazonaws.com/");


might benefit from using

aws-sdk-java-v2/utils/src/main/java/software/amazon/awssdk/utils/HostnameValidator.java

Lines 31 to 33 in 8a6a76c

public static void validateHostnameCompliant(String hostnameComponent, String paramName, String object) {

validateHostnameCompliant(hostnameComponent, paramName, object, DEFAULT_HOSTNAME_COMPLIANT_PATTERN);

}

alternatively, build using the URI constructor will also validate it for correctness

dagnir · 2026-06-26T20:20:52Z

+    private final String body;
+    private final String contentType;


The ctor is private; are these necessary?

dagnir · 2026-06-26T20:23:51Z

+ * Resolves the regional STS endpoint ({@code https://sts.<region>.amazonaws.com/}) used by the CRaC HTTP-client warm-up.
+ *


Is this class intended to resolve other service endpoints in the future?

dagnir · 2026-06-26T20:25:49Z

+ * matters for JIT priming.
+ */
+@SdkInternalApi
+public final class WarmUpRequest {


Not really sure about the usefulness of this class. Does it make more sense to just have a utility class/factory just creates the HttpExecuteRequest directly?

dagnir · 2026-06-26T20:31:48Z

+public class Apache5HttpClientWarmUpTest {
+
+    @Rule
+    public WireMockRule mockServer = new WireMockRule(0);


A separate centralized package would be great, but maybe we can have a dedicated test package for testing CRaC components instead of using http-client-tests

joviegas requested a review from a team as a code owner June 26, 2026 00:08

feat(sdk-core): add sync HTTP-client warm-up to SdkWarmUp.prime() for…

adaf1a0

… CRaC priming

joviegas force-pushed the joviegas/crac_warmup_orchestration_partB branch 2 times, most recently from e4dfbde to 5b172b4 Compare June 26, 2026 15:17

Updated tests

82c723b

joviegas force-pushed the joviegas/crac_warmup_orchestration_partB branch from 5b172b4 to 82c723b Compare June 26, 2026 15:29

restructure test and comments

311aff8

joviegas force-pushed the joviegas/crac_warmup_orchestration_partB branch 2 times, most recently from bbf82e3 to 44b6b00 Compare June 26, 2026 16:43

joviegas commented Jun 26, 2026

View reviewed changes

Fixed checkstyle issues

2f5b864

joviegas force-pushed the joviegas/crac_warmup_orchestration_partB branch from 44b6b00 to 2f5b864 Compare June 26, 2026 18:26

dagnir reviewed Jun 26, 2026

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feat(sdk-core): add sync HTTP-client warm-up to SdkWarmUp.prime() for CRaC priming#7080

feat(sdk-core): add sync HTTP-client warm-up to SdkWarmUp.prime() for CRaC priming#7080
joviegas wants to merge 4 commits into
feature/master/crac_auto_priming_supportfrom
joviegas/crac_warmup_orchestration_partB

joviegas commented Jun 26, 2026 •

edited

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	public static void validateHostnameCompliant(String hostnameComponent, String paramName, String object) {
	validateHostnameCompliant(hostnameComponent, paramName, object, DEFAULT_HOSTNAME_COMPLIANT_PATTERN);
	}

		* Resolves the regional STS endpoint ({@code https://sts.<region>.amazonaws.com/}) used by the CRaC HTTP-client warm-up.
		*

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joviegas commented Jun 26, 2026 •

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